package com.jinxinol.core.common.verifycode;

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;

import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.sun.image.codec.jpeg.JPEGCodec;
import com.sun.image.codec.jpeg.JPEGImageEncoder;

/**
 * 
 * @company Jinxin Computer Corp.
 * @author Chenbing
 * @email wwwchenbing@gmail.com
 * @description 验证码生成器，使用此类需要将表单里的验证码输入框的name属性设为"verifycode" 
 * @date 2012-8-12
 */
public class VerifyCodeGenerator { 
     
    private static final VerifyCodeGenerator generator = new VerifyCodeGenerator(); 
     
    private final String ATTRIBUTE_NAME = "verifycode"; 
    //图片的宽度 
    private final int WIDTH = 15; 
    //图片的高度 
    private final int HEIGHT = 22; 
    //字符串长度 
    private final int CODE_LENGTH = 4; 
    //随机字符串范围 
    private final String RAND_RANGE = "abcdefghijklmnopqrstuvwxyz" 
        + "ABCDEFGHIJKLMNOPQRSTUVWXYZ" 
        + "1234567890";
     
    private final char[] CHARS = RAND_RANGE.toCharArray(); 
     
    private Random random = new Random(); 
     
    private VerifyCodeGenerator(){} 
     
    public static VerifyCodeGenerator getInstance(){ 
        return generator; 
    } 
     
    /** 
     * 生成随机字符串 
     * @return 随机字符串 
     */ 
    private String getRandString(){ 
        StringBuilder sb = new StringBuilder(); 
        int seed = (int)(System.nanoTime() % CHARS.length);
        seed = (seed == 0) ? CHARS.length : seed;
        for (int i = 0; i < CODE_LENGTH; i++) 
            sb.append(CHARS[random.nextInt(seed)]); 
        return sb.toString(); 
    } 
     
    /** 
     * 生成随机颜色 
     * @param ll 产生颜色值下限(lower limit) 
     * @param ul 产生颜色值上限(upper limit) 
     * @return 生成的随机颜色对象 
     */ 
    private Color getRandColor(int ll, int ul){ 
        if (ll > 255) ll = 255; 
        if (ll < 1) ll = 1; 
        if (ul > 255) ul = 255; 
        if (ul < 1) ul = 1; 
        if (ul == ll) ul = ll + 1; 
        int r = random.nextInt(ul - ll) + ll; 
        int g = random.nextInt(ul - ll) + ll; 
        int b = random.nextInt(ul - ll) + ll; 
        Color color = new Color(r,g,b); 
        return color; 
    } 
     
    /** 
     * 生成指定字符串的图像数据 
     * @param verifyCode 即将被打印的随机字符串 
     * @return 生成的图像数据 
     * */ 
    private BufferedImage getImage(String verifyCode){ 
         
        BufferedImage image = new BufferedImage(WIDTH * CODE_LENGTH, HEIGHT, BufferedImage.TYPE_INT_RGB); 
         
        //获取图形上下文 
        Graphics graphics = image.getGraphics(); 
         
        //设置背景色 
        graphics.setColor(getRandColor(1,200)); 
        //填充背景色 
        graphics.fillRect(0, 0, WIDTH * CODE_LENGTH, HEIGHT); 
         
        //设置边框颜色 
        graphics.setColor(new Color(216,191,216)); 
        //画边框 
        for (int i=0; i<2; i++) 
            graphics.drawRect(i, i, WIDTH * CODE_LENGTH - i * 2 - 1, HEIGHT - i * 2 - 1); 
         
        //设置随机干扰线条颜色 
        graphics.setColor(getRandColor(50,100)); 
        //产生50条干扰线条 
        for (int i=0; i<10; i++){ 
            int x1 = random.nextInt(WIDTH * CODE_LENGTH - 4) + 2; 
            int y1 = random.nextInt(HEIGHT - 4) + 2; 
            int x2 = random.nextInt(WIDTH * CODE_LENGTH - 2 - x1) + x1; 
            int y2 = y1; 
            graphics.drawLine(x1, y1, x2, y2); 
        } 
         
        //设置字体 
        graphics.setFont(new Font("Times New Roman", Font.PLAIN, 18)); 
        //画字符串 
        for (int i=0; i<this.CODE_LENGTH; i++){ 
            String temp = verifyCode.substring(i, i+1); 
            graphics.setColor(getRandColor(100,255)); 
            graphics.drawString(temp, 13 * i + 6, 16); 
        } 
         
        //图像生效 
        graphics.dispose(); 
         
        return image; 
    } 
     
    /** 
     * 将验证码的图像输出 
     * @param request 用户的请求对象 
     * @param response 用户的响应对象 
     * */ 
    public void printImage(HttpServletRequest request, 
            HttpServletResponse response){ 
        //将ContentType设为"image/jpeg"，让浏览器识别图像格式。 
        response.setContentType("image/jpeg"); 
        //设置页面不缓存 
        response.setHeader("Pragma", "No-cache"); 
        response.setHeader("Cache-Control", "no-cache"); 
        response.setDateHeader("Expires", 2000); 
         
        //获得随机验证码 
        String verifyCode = this.getRandString(); 
        String str = "ssss"; 
        for(int i=0; i<10; i++) 
            str = str + str; 
        //获得验证码的图像数据 
        BufferedImage bi = this.getImage(verifyCode); 
        //把验证码存入session 
        request.getSession().setAttribute(ATTRIBUTE_NAME, verifyCode); 
        try{ 
            //获得Servlet输出流 
            ServletOutputStream outStream = response.getOutputStream(); 
            //创建可用来将图像数据编码为JPEG数据流的编码器 
            JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(outStream); 
            //将图像数据进行编码 
            encoder.encode(bi); 
            //强行将缓冲区的内容输入到页面 
            outStream.flush(); 
            //关闭输出流 
            outStream.close(); 
        }catch(IOException ex){ 
            ex.printStackTrace(); 
        } 
    } 
     
    /** 
     * 检查输入的验证码是否正确，若用户输入的验证码与生成的验证码相符则返回true，否则返回false。 
     * @param request 用户的请求对象 
     * @return 验证结果 
     * */ 
    public boolean check(HttpServletRequest request){ 
        if (((String)request.getParameter(ATTRIBUTE_NAME)) 
                .equalsIgnoreCase((String)request.getSession().getAttribute(ATTRIBUTE_NAME))){ 
            request.getSession().removeAttribute(ATTRIBUTE_NAME); 
            return true; 
        } 
        return false; 
    } 
}